PM / devfreq: exynos4_bus: honor RCU lock usage

OPP pointers cannot be expected to be valid beyond the boundary
of rcu_read_lock and rcu_read_unlock. Unfortunately, the current
exynos4 busfreq driver does not honor the usage constraint and stores
the OPP pointer in struct busfreq_data. This could potentially
become invalid later such as: across devfreq opp change decisions,
resulting in unpredictable behavior.

To fix this, we introduce a busfreq specific busfreq_opp_info
structure which is used to handle OPP information. OPP information
is de-referenced to voltage and frequency pairs as needed into
busfreq_opp_info structure and used as needed.

Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/devfreq/exynos4_bus.c b/drivers/devfreq/exynos4_bus.c
index 80c745e83082bf6d9dade7a81dffbb89931632a7..46d94e9e95b53ae033af012ef745822e0b7f5ccd 100644 (file)
--- a/drivers/devfreq/exynos4_bus.c
+++ b/drivers/devfreq/exynos4_bus.c
@@ -73,6 +73,16 @@ enum busclk_level_idx {
 #define EX4210_LV_NUM  (LV_2 + 1)
 #define EX4x12_LV_NUM  (LV_4 + 1)
 
+/**
+ * struct busfreq_opp_info - opp information for bus
+ * @rate:      Frequency in hertz
+ * @volt:      Voltage in microvolts corresponding to this OPP
+ */
+struct busfreq_opp_info {
+       unsigned long rate;
+       unsigned long volt;
+};
+
 struct busfreq_data {
        enum exynos4_busf_type type;
        struct device *dev;
@@ -80,7 +90,7 @@ struct busfreq_data {
        bool disabled;
        struct regulator *vdd_int;
        struct regulator *vdd_mif; /* Exynos4412/4212 only */
-       struct opp *curr_opp;
+       struct busfreq_opp_info curr_oppinfo;
        struct exynos4_ppmu dmc[2];
 
        struct notifier_block pm_notifier;
@@ -296,13 +306,14 @@ static unsigned int exynos4x12_clkdiv_sclkip[][3] = {
 };
 
 
-static int exynos4210_set_busclk(struct busfreq_data *data, struct opp *opp)
+static int exynos4210_set_busclk(struct busfreq_data *data,
+                                struct busfreq_opp_info *oppi)
 {
        unsigned int index;
        unsigned int tmp;
 
        for (index = LV_0; index < EX4210_LV_NUM; index++)
-               if (opp_get_freq(opp) == exynos4210_busclk_table[index].clk)
+               if (oppi->rate == exynos4210_busclk_table[index].clk)
                        break;
 
        if (index == EX4210_LV_NUM)
@@ -361,13 +372,14 @@ static int exynos4210_set_busclk(struct busfreq_data *data, struct opp *opp)
        return 0;
 }
 
-static int exynos4x12_set_busclk(struct busfreq_data *data, struct opp *opp)
+static int exynos4x12_set_busclk(struct busfreq_data *data,
+                                struct busfreq_opp_info *oppi)
 {
        unsigned int index;
        unsigned int tmp;
 
        for (index = LV_0; index < EX4x12_LV_NUM; index++)
-               if (opp_get_freq(opp) == exynos4x12_mifclk_table[index].clk)
+               if (oppi->rate == exynos4x12_mifclk_table[index].clk)
                        break;
 
        if (index == EX4x12_LV_NUM)
@@ -576,11 +588,12 @@ static int exynos4x12_get_intspec(unsigned long mifclk)
        return -EINVAL;
 }
 
-static int exynos4_bus_setvolt(struct busfreq_data *data, struct opp *opp,
-                              struct opp *oldopp)
+static int exynos4_bus_setvolt(struct busfreq_data *data,
+                              struct busfreq_opp_info *oppi,
+                              struct busfreq_opp_info *oldoppi)
 {
        int err = 0, tmp;
-       unsigned long volt = opp_get_voltage(opp);
+       unsigned long volt = oppi->volt;
 
        switch (data->type) {
        case TYPE_BUSF_EXYNOS4210:
@@ -595,11 +608,11 @@ static int exynos4_bus_setvolt(struct busfreq_data *data, struct opp *opp,
                if (err)
                        break;
 
-               tmp = exynos4x12_get_intspec(opp_get_freq(opp));
+               tmp = exynos4x12_get_intspec(oppi->rate);
                if (tmp < 0) {
                        err = tmp;
                        regulator_set_voltage(data->vdd_mif,
-                                             opp_get_voltage(oldopp),
+                                             oldoppi->volt,
                                              MAX_SAFEVOLT);
                        break;
                }
@@ -609,7 +622,7 @@ static int exynos4_bus_setvolt(struct busfreq_data *data, struct opp *opp,
                /*  Try to recover */
                if (err)
                        regulator_set_voltage(data->vdd_mif,
-                                             opp_get_voltage(oldopp),
+                                             oldoppi->volt,
                                              MAX_SAFEVOLT);
                break;
        default:
@@ -626,17 +639,26 @@ static int exynos4_bus_target(struct device *dev, unsigned long *_freq,
        struct platform_device *pdev = container_of(dev, struct platform_device,
                                                    dev);
        struct busfreq_data *data = platform_get_drvdata(pdev);
-       struct opp *opp = devfreq_recommended_opp(dev, _freq, flags);
-       unsigned long freq = opp_get_freq(opp);
-       unsigned long old_freq = opp_get_freq(data->curr_opp);
+       struct opp *opp;
+       unsigned long freq;
+       unsigned long old_freq = data->curr_oppinfo.rate;
+       struct busfreq_opp_info new_oppinfo;
 
-       if (IS_ERR(opp))
+       rcu_read_lock();
+       opp = devfreq_recommended_opp(dev, _freq, flags);
+       if (IS_ERR(opp)) {
+               rcu_read_unlock();
                return PTR_ERR(opp);
+       }
+       new_oppinfo.rate = opp_get_freq(opp);
+       new_oppinfo.volt = opp_get_voltage(opp);
+       rcu_read_unlock();
+       freq = new_oppinfo.rate;
 
        if (old_freq == freq)
                return 0;
 
-       dev_dbg(dev, "targetting %lukHz %luuV\n", freq, opp_get_voltage(opp));
+       dev_dbg(dev, "targetting %lukHz %luuV\n", freq, new_oppinfo.volt);
 
        mutex_lock(&data->lock);
 
@@ -644,17 +666,18 @@ static int exynos4_bus_target(struct device *dev, unsigned long *_freq,
                goto out;
 
        if (old_freq < freq)
-               err = exynos4_bus_setvolt(data, opp, data->curr_opp);
+               err = exynos4_bus_setvolt(data, &new_oppinfo,
+                                         &data->curr_oppinfo);
        if (err)
                goto out;
 
        if (old_freq != freq) {
                switch (data->type) {
                case TYPE_BUSF_EXYNOS4210:
-                       err = exynos4210_set_busclk(data, opp);
+                       err = exynos4210_set_busclk(data, &new_oppinfo);
                        break;
                case TYPE_BUSF_EXYNOS4x12:
-                       err = exynos4x12_set_busclk(data, opp);
+                       err = exynos4x12_set_busclk(data, &new_oppinfo);
                        break;
                default:
                        err = -EINVAL;
@@ -664,11 +687,12 @@ static int exynos4_bus_target(struct device *dev, unsigned long *_freq,
                goto out;
 
        if (old_freq > freq)
-               err = exynos4_bus_setvolt(data, opp, data->curr_opp);
+               err = exynos4_bus_setvolt(data, &new_oppinfo,
+                                         &data->curr_oppinfo);
        if (err)
                goto out;
 
-       data->curr_opp = opp;
+       data->curr_oppinfo = new_oppinfo;
 out:
        mutex_unlock(&data->lock);
        return err;
@@ -702,7 +726,7 @@ static int exynos4_bus_get_dev_status(struct device *dev,
 
        exynos4_read_ppmu(data);
        busier_dmc = exynos4_get_busier_dmc(data);
-       stat->current_frequency = opp_get_freq(data->curr_opp);
+       stat->current_frequency = data->curr_oppinfo.rate;
 
        if (busier_dmc)
                addr = S5P_VA_DMC1;
@@ -933,6 +957,7 @@ static int exynos4_busfreq_pm_notifier_event(struct notifier_block *this,
        struct busfreq_data *data = container_of(this, struct busfreq_data,
                                                 pm_notifier);
        struct opp *opp;
+       struct busfreq_opp_info new_oppinfo;
        unsigned long maxfreq = ULONG_MAX;
        int err = 0;
 
@@ -943,18 +968,29 @@ static int exynos4_busfreq_pm_notifier_event(struct notifier_block *this,
 
                data->disabled = true;
 
+               rcu_read_lock();
                opp = opp_find_freq_floor(data->dev, &maxfreq);
+               if (IS_ERR(opp)) {
+                       rcu_read_unlock();
+                       dev_err(data->dev, "%s: unable to find a min freq\n",
+                               __func__);
+                       return PTR_ERR(opp);
+               }
+               new_oppinfo.rate = opp_get_freq(opp);
+               new_oppinfo.volt = opp_get_voltage(opp);
+               rcu_read_unlock();
 
-               err = exynos4_bus_setvolt(data, opp, data->curr_opp);
+               err = exynos4_bus_setvolt(data, &new_oppinfo,
+                                         &data->curr_oppinfo);
                if (err)
                        goto unlock;
 
                switch (data->type) {
                case TYPE_BUSF_EXYNOS4210:
-                       err = exynos4210_set_busclk(data, opp);
+                       err = exynos4210_set_busclk(data, &new_oppinfo);
                        break;
                case TYPE_BUSF_EXYNOS4x12:
-                       err = exynos4x12_set_busclk(data, opp);
+                       err = exynos4x12_set_busclk(data, &new_oppinfo);
                        break;
                default:
                        err = -EINVAL;
@@ -962,7 +998,7 @@ static int exynos4_busfreq_pm_notifier_event(struct notifier_block *this,
                if (err)
                        goto unlock;
 
-               data->curr_opp = opp;
+               data->curr_oppinfo = new_oppinfo;
 unlock:
                mutex_unlock(&data->lock);
                if (err)
@@ -1027,13 +1063,17 @@ static int exynos4_busfreq_probe(struct platform_device *pdev)
                }
        }
 
+       rcu_read_lock();
        opp = opp_find_freq_floor(dev, &exynos4_devfreq_profile.initial_freq);
        if (IS_ERR(opp)) {
+               rcu_read_unlock();
                dev_err(dev, "Invalid initial frequency %lu kHz.\n",
                        exynos4_devfreq_profile.initial_freq);
                return PTR_ERR(opp);
        }
-       data->curr_opp = opp;
+       data->curr_oppinfo.rate = opp_get_freq(opp);
+       data->curr_oppinfo.volt = opp_get_voltage(opp);
+       rcu_read_unlock();
 
        platform_set_drvdata(pdev, data);